Joint replacement surgery is a common orthopedic procedure for joint such as the shoulder, hip, knee, ankle and wrist. Prior to implanting prosthetic components in a joint of a patient, a surgeon generally has to resect at least a portion of the patient's native bone in order to create a recess or cavity for receiving at least a portion of the prosthetic components being implanted. During the process of resecting bone, a surgeon generally only resects the amount of bone that is needed in order to implant the prosthetic components in the joint replacement surgery properly. Once native bone is resected from a joint, it generally can no longer be used in the joint. Thus, the surgeon attempts to maintain as much native structural integrity of the joint as he or she can during the resection process.
When prosthetic components fail for any one of a variety of reasons, a revision procedure is often necessary. An issue generally encountered by surgeons replacing joints during a revision procedure is the loss of native bone near the joint being replaced. Defects in a bone adjacent a joint, such as the hip or knee, may occur due to wear and arthritis of the joint, congenital deformity, and following the removal of a failed prosthetic component. When the failed prosthetic component or components are removed from the joint during a revision procedure, it is common for there to have been further native bone loss in the area adjacent the original implant position of the prosthetic component or components. This bone loss is typically due to movement of the component or components after implantation or even degeneration or further degeneration of the bone, which can form bone voids that have unpredictable and non-uniform shapes.
When bone voids are observed in either the proximal tibia or distal femur, or both, it is standard surgical practice to fill those voids as part of the surgical procedure. The preferred practice is to fill those voids with weight bearing void fillers, typically made of an implant-grade metal such as titanium. These void fillers may be referred to as metaphyseal reconstruction devices (MRD). The name MRD more accurately reflects functions such as weight bearing that these devices provide.
Because the bone voids are typically irregular in shape, preparation of the bone void area is typically required prior to implantation of the MRD. This preparation (typically by reaming, broaching or milling) ensures there is sufficient room in the bone cavity for the MRD. An accurate fit between the shaped bone cavity and the MRD is important for establishing joint line, and allowing for weight bearing and bone remodeling during the recovery process.
Different methods are commonly used to attempt to prepare the bone void area to create an accurate fit between the shaped bone cavity and the MRD. One method is to ream along the intramedullary (IM) axis, followed by broaching. Another method is to ream on the IM axis, followed by freehand burr or rongeur bone removal, which may also be followed by broaching. Problems with these methods include that reaming is performed on the IM axis only, so that void areas at a distance from the IM axis, which commonly occur, can only be resected using manual methods. Moreover, broaching generally has at least two problems. First, a manual operation can be time consuming, particularly in cases of sclerotic bone, which exposes the patient to an increased risk of infection and a longer recovery. Second, in the case of large bone voids, broaching generally needs to be performed in a multi-step process because attempting to remove high volumes of bone in a single broaching step generally requires high impact forces to the bone. Also, freehand bone removal, either powered or unpowered, such as by burr or rongeur, often does not produce accurate cavity shapes to receive predefined prosthetic components. A typical result is that areas remain where the outer walls of the MRD do not contact the cavity, which may lead to undesirable stress distribution and possible loss of bone regrowth. Also typical is the time consuming requirement of iterative bone removal, with multiple checks against the MRD, to obtain a correct fit.
Thus, there is a need for a surgical reaming instrument that creates accurate bone cavity geometries in minimal time and that minimizes the necessity for freehand bone removal. There is also a need for enabling surgeons to create bone cavities with a fully guided system.